Durbin was taking questions about Supreme Court nominee Sonia Sotomayor and whether she would be an activist justice or whether she would focus on only interpreting the law.

Would Sotomayor, the anchor asked, be like Chief Justice John Roberts and act only as an umpire of law?

"Well let me just you something," Durbin said, "There have been a lot of questions raised about Judge Roberts's strike zone."

The umpire metaphor comes directly from Roberts's confimation hearings. He said at the time: "Judges are like umpires...Umpires don't make the rules. They apply them. The role of an umpire and a judge is critical. They make sure everybody plays by the rules. But it is a limited role. Nobody ever went to a ballgame to see the umpire."

Durbin's criticism is likely rooted in this recent New Yorker story by Jeffrey Toobin. In it, Toobin argues that Roberts has not stepped into that umpire role but, rather, has been the voice of the Republican Party on the high court.